The present invention relates generally to storage tanks for storing fluid materials, and in particular, to an improved piston for use in extruding the fluid stored therein.
Storage tanks, particularly those used in the transportation of viscous, fluid materials, typically comprise a piston that moves along a longitudinal axis in the tank to push the materials through and out an opening in one end of the tank. The piston typically includes a seal that “wipes” the interior surface of the tank, and prevents the backflow of material as the piston moves along the longitudinal axis. Problems may arise, however, when the tank is not perfectly round or has imperfections in the surface. For example, gaps may form between the seal and the interior surface of the tank allowing material to squeeze past the piston. Therefore, a mechanism is needed that will maintain a firm contact between the seal and the inner surface of the tank without creating unnecessary friction, thereby preventing the backflow of material past the piston.